This invention relates to fractal antenna(s) (or antennae). More particularly, one embodiment of this invention relates to a vehicle windshield including a fractal antenna(s). Another embodiment of this invention relates to a multiband fractal antenna. Yet another embodiment of this invention relates to an array of fractal antennas.
Generally speaking, antennas radiate and/or receive electromagnetic signals. Design of antennas involves balancing of parameters such as antenna size, antenna gain, bandwidth, and efficiency.
Most conventional antennas are of Euclidean design/geometry, where the closed antenna area is directly proportional to the antenna perimeter. Thus, for example, when the length of a Euclidean square is increased by a factor of three, the enclosed area of the antenna is increased by a factor of nine. Unfortunately, Euclidean antennas are less than desirable as they are susceptible to high Q factors, and become inefficient as their size gets smaller.
Characteristics (e.g., gain, directivity, impedance, efficiency) of Euclidean antennas are a function of the antenna""s size to wavelength ratio. Euclidean antennas are typically designed to operate within a narrow range (e.g., 10-40%) around a center frequency xe2x80x9cfcxe2x80x9d which in turn dictates the size of the antenna (e.g., half or quarter wavelength). When the size of a Euclidean antenna is made much smaller than the operating wavelength (xcex), it becomes very inefficient because the antenna""s radiation resistance decreases and becomes less than its ohmic resistance (i.e., it does not couple electromagnetic excitations efficiently to free space). Instead, it stores energy reactively within its vicinity (reactive impedance Xc). These aspects of Euclidean antennas work together to make it difficult for small Euclidean antennas to couple or match to feeding or excitation circuitry, and cause them to have a high Q factor (lower bandwidth). Q factor may be defined as approximately the ratio of input reactance to radiation resistance (Q≈Xin/R_r). The Q factor may also be defined as the ratio of average stored electric energies (or magnetic energies stored) to the average radiated power. Q can be shown to be inversely proportional to bandwidth. Thus, small Euclidean antennas have very small bandwidth, which is of course undesirable (e.g., tuning circuitry may be needed).
Many known Euclidean antennas are based upon closed-loop shapes. Unfortunately, when small in size, such loop-shaped antennas are undesirable because, as discussed above, e.g., radiation resistance decreases significantly when the antenna size/area is shortened/dropped. This is because the physical area (xe2x80x9cAxe2x80x9d) contained within the loop-shaped antenna""s contour is related to the latter""s perimeter. Radiation resistance (R_r) of a circular (i.e., loop-shaped) Euclidean antenna is defined by (xe2x80x9ckxe2x80x9d is a constant):
Rxe2x80x94r=xcex7(2/3)xcfx80(kA/xcex)2=20xcfx802(C/xcex)4xe2x80x83xe2x80x83(1)
Since ohmic resistance (R_c) is only proportional to perimeter (C), then for C less than 1, the ohmic resistance (R_c) is greater than the radiation resistance (R_r) and the antenna is highly inefficient. This is generally true for any small circular Euclidean antenna. In this regard, it is stated in U.S. Pat. No. 6,104,349 (hereby incorporated herein by reference) at column 2, lines 14-19 that xe2x80x9csmall-sized antennas will exhibit a relatively large ohmic resistance O and a relatively small radiation resistance R, such that resultant low efficiency defeats the use of the small antenna.xe2x80x9d
Fractal geometry is a non-Euclidean geometry which can be used to overcome the aforesaid problems with small Euclidean antennas. Again, see the ""349 Patent in this regard. Radiation resistance R_r of a fractal antenna decreases as a small power of the perimeter (C) compression, with a fractal loop or island always having a substantially higher radiation resistance than a small Euclidean loop antenna of equal size. Accordingly, fractals are much more effective than Euclideans when small sizes are desired. Fractal geometry may be grouped into (a) random fractals, which may be called chaotic or Brownian fractals and include a random noise component, and (b) deterministic or exact fractals. In deterministic fractal geometry, a self-similar structure results from the repetition of a design or motif (or xe2x80x9cgeneratorxe2x80x9d) (i.e., self-similarity and structure at all scales). In deterministic or exact self-similarity, fractal antennas may be constructed through recursive or iterative means as in the ""349 Patent. In other words, fractals are often composed of many copies of themselves at different scales, thereby allowing them to defy the classical antenna performance constraint which is size to wavelength ratio.
Recent growth in technology such as the Internet, cellular telecommunications, and the like has led to personal users desiring wireless access for: Internet access, cell phones, pagers, personal digital assistants, etc., while competing types of wireless broadband such as TDMA (time division multiple access), CDMA (code division multiple access) and GSM are being pushed by wireless manufacturers. Unfortunately, current vehicle antenna systems do not have the capability of efficiently enabling such desired wireless access.
In view of the above, it will be apparent that there exists a need in the art for a vehicle antenna system that enables efficient access to the Internet, cell phones, pagers, personal digital assistants, radio, and/or the like. There also exists a need in the art for a multiband fractal antenna. These and other needs which will become apparent to the skilled artisan from a review of the instant application are achieved by the instant invention(s).
An object of this invention is to provide a vehicle windshield including a fractal antenna therein.
Another object of this invention is to provide a system including an array of fractal antennas (or antennae).
Another object of this invention is to provide a multiband fractal antenna.
Another object of this invention is to fulfill one or more of the above-listed objects and/or needs.
In certain example embodiments, this invention fulfills one or more of the above-listed objects and/or needs by providing a vehicle windshield comprising:
first and second substrates laminated to one another via at least a polymer inclusive interlayer; and
at least one fractal antenna located at least partially between said first and second substrates.
In other embodiments of this invention, one or more of the above-listed needs and/or objects is fulfilled by providing a method of making a vehicle windshield, the method comprising:
providing first and second substrates;
forming a first conductive layer on the first substrate;
forming a resist on the first substrate over the first conductive layer;
patterning the first conductive layer into a shape of a fractal antenna using
the resist, thereby leaving the fractal antenna on the first substrate; and laminating the first substrate with fractal antenna thereon to the second substrate via a polymer inclusive interlayer.
In still further embodiments of this invention, one or more of the above-listed needs is fulfilled by providing a multiband fractal antenna comprising
a first group of isosceles triangular shaped antenna portions of a first size;
a second group of isosceles triangular shaped antenna portions of a second size larger than said first size;
a third triangular shaped isosceles antenna portion of a third size larger than said first and second sizes;
wherein each of said triangular shaped antenna portions of said first and second groups is located within a periphery of said third triangular shaped antenna portion so as to provide a multiband fractal antenna.
In certain embodiments, said first group of triangular shaped antenna portions transmits and/or receives at a first frequency band, said second group of triangular shaped antenna portions transmits and/or receives at a second frequency band different than said first band, and said third triangular shaped antenna portion transmits and/or receives at a third frequency band different than said first and second bands. The portions may be shaped as isosceles triangles in certain embodiments.
Certain embodiments of this invention further fulfill one or more of the above-listed objects and/or needs by providing a method of making a vehicle window, the method comprising:
forming a fractal conductive antenna layer on a polymer inclusive film, said polymer inclusive film also supporting an adhesive layer and a release layer;
removing the release layer, and adhering the polymer inclusive film with the fractal conductive antenna layer thereon to a substrate; and
laminating the substrate to another substrate via a polymer inclusive interlayer in the process of forming a vehicle window.
Other embodiments fulfill one or more of the above-listed needs by providing a method of making a vehicle window, the method comprising:
forming a fractal layer on a polymer inclusive layer; and
laminating first and second substrates to one another via the polymer inclusive layer so that following said laminating the fractal layer is sandwiched between the substrates.